Magnetic ore separator for wet and other operations



Feb. 20, 1934. v P. H. THOMAS 1 memmc om: SEPARATOR FOR war AND OTHEROPERATIONS Filed May 10, 1950 3 Sheets-Sheet 1 INVENTOR Fig.7 W 4 Feb.20, 1934. 1,948,089

MAGNETIC ORE SEPARATOR FOR WET AND OTHER OPERATIONS P. H; THOMAS Feb.20, 1934. P. H. THoMAs 1,948,080

MAGNETIC ORE SEPAR ATOR FOR WET AND OTHER OPERATIONS Filed May 10, 19303 Sheets-Sheet 3 Patented Feb. 20, 1934 UNITED STATES PATENT OFFICEMAGNETIC ORE SEPARATOR FOR WET AND OTHER OPERATIONS My invention relatesto the process in which a separation of a magnetizable or partiallymagnetizable material from a mixture containing unmagnetizable materialis accomplished by the use of a magnetic field and embodies moreparticularly the use of electromagnets so arranged and manipulated withregard to the feed of the mixed material thatboth large quantities ofmaterial can be handled and at the same time a thorough exposure of allthe feed to the extracting influence of the magnetism is secured withthe result that large tonnage capacity is obtained with a. simultaneoussatisfactory recovery of the magnetizable and/or slightly magnetizablematerial with a high degree of purity. My invention also contemplates inconnection with the handling of wet material means for washing themagnetizable materialsuch as concentrate-while under the influence ofthe magnetic field to clean it and thereby increase its percentage ofmetal content and also the dewatering of the recovered material, wheresuch a result is advantageous. In virtue of the long distance throughwhich the pulp passes while under the magnetic influence, and thefavorable magnetic design as well as the fact that the material is keptwithin the desired distance of the magnet pole pieces together withother favorable features hereinafter described it is possible by thisinvention to get very much larger tonnage capacities in a magneticseparator than heretofore and to retain weakly magnetizable particlesand even to concentrate some ores not usually treated magnetically;provided such ores have some magnetizable quality. It is also possibleto wash the concentrate much more thoroughly without losing values. Myinvention has other novel features which will appear hereinafter. I

I have shown in Figs. 1 to '7 a favorable embodiment of my invention,where magnetic ore requiring concentration is to be handled by the wetprocess. Fig. 1 is a vertical section of the complete apparatus on theline F, F, Fig. 2, certain parts being omitted, showing the meansprovided for separating the magnetizable material from the gangue; Fig.2 is an enlarged cross section of a portion of the enclosed channelthrough which the pulverized ore or pulp is passed for the purpose ofconcentration; Fig. 3 is an enlarged detail of the seal used at thesides of the enclosed channel showing certain structural details. Fig. 4shows the shape and construction of the magnetic pole pieces; Figs. 5and 6 show certain details of construction used to adjust the dimensionsand position of the enclosed channel and hold it securely in position;Fig. '7 is a section showing 'a detail of the lining of the channel.Fig. 8 is an alternative form of pole piece and Figs. 9 and 10 are aside view and section of an alternative form of magnet construction.

Referring more in detail to the construction shown in Figs. 1 to 7 itmay be pointed out that in the process of concentration the pulp,a wet"mixture of ground material, such as the pulp prepared in extractingmagnetite ore,-which car- 5 ries an excess of water is passed through anenclosed channel constructed to conform more or less to the arc of acircle, one face of this channel corresponding to the outer surface of arevolving wheel. partly covered by a series of iron pole pieces whichproduce a strong magnetic field in the enclosed channel and the pulp inpassing through this field has its magnetizable material so strongly atetracted that it will cling to the belt which forms 7"; one side of thechannel and moves with the revolving wheel. As the pulp emerges fromthis channel which is made long enough to give time for the desiredportion of the magnetizable material to become drawn to the belt, thenon-magnetic part of the mixture is free to leave themagnetizable part,leaving the latter purified and concentrated. As shown in the drawingsthe pulp moves in a more or less downward direction as it leaves theenclosed channel and the force of gravity and. centrifugal force bothtend to cause the nonmagnetic material or waste to leave thosurface ofthe wheel on which the concentrate has been accumulated.

In this construction I have shown a belt, which may well be of thinrubber running on the periphery of the wheel on top of the iron polepieces and also over a smaller idler pulley on a separate shaft. Thisbelt comes between the iron pole pieces and the pulp in the enclosedchannel and it is upon this belt that the concentrate is held by themagnetic field. This belt emerges from the channel at a-point wherethemagnetizable material is still under the influence of the mag- 10o neticpole pieces and only at a later point leaves the surface of the wheel topass over the idler at which point it carries theconcentrate out of themagnetic field.

In these Figs. 1 to 7 the revolving wheel is shown at 1, being carriedby the shaft 2. The enclosed channel through which the pulp passes isshown at 3, this channel being formed by the cover back or shield 29,and the belt 5. The pulp to be treated is accumulated in the headtanlrfi, 11

This wheel surface is covered or 70 through the launder *1 and aconstant head is maintained in the head tank 6 by the overflow 8 whichshould be made adjustable and of suffiart.

I have shown 3 nozzles 9a, 9b, 9c, feeding pulp to the channel 3, I willpoint out that the position of the nozzle 9n must not be located so farto the left that the material discharged will not enter the channel 3.If the wheel revolves in the direction of the solid arrow "the motion ofthe wheel and the spouting velocity of the pulp work together but whenthe rotation of the wheel is in the direction of the dotted arrow, thewheel velocity acts against the spouting velocity of the pulp. Thelocation of the nozzle 9a toward the left increases the distancetravelled by the pulp in the channel and the time required-which isusually favorable for the operation.

By the use of more than one nozzle I am able 2 to have the magneticfield operate upon a portion of the pulp first, whichis favorablein'some cases to a more perfect action. The pulp introduced at the othernozzles then finds the concentration process well advanced on the firstportions of the pulp introduced. These nozzles are so shapedusually aslong narrow slots,as to distribute the pulp across the entire width ofthe channel.

The channel 3 has its discharge opening near the point 10, there thetailings are free to fall into the launder or drain l1. The partition orbaflle 11a serves to aid this action.

I use a jet of clear water from a nozzle 22 located beyond the bafiie11a to wash the concentrate and to remove any remaining impurities, organgue including the dirty water adhering to it. The concentrate beingstill under the re-.

straining influence of the magnetic field will not be easily washed ofi.The material caught in the launder 23 maybe discharged to waste ortreated p further if desirable.

It will'be noted that the chutes leading to the nozzles 9a, 9b, 90, haveone side vertical and one side steeply inclined. As a result the heavierparticles which are usually the valuable material will tend to settle onthe inclined side and'be fed at the bottom of the jet onto the belt.They will thus become fixed without being dragged through the liquidpulp and the chance of mechanically entraining gangue will be reduced.At a point near 12 the belt leaves the surface of, the pole pieces topass over the idler pulley 13 and the concentrate is removed from theinfluence of the magnetic fieldand is free to drop off onto the hopper14 or be washed off by the water from nozzles l5.15. In some. cases Iuse nozzles 16, 16 for this purpose operating on the belt afterit leavesthe idler 13. .In some cases I use scrapers 1'7, 17a to remove theconcentrate. I may use insteadof a scraper a revolving brush revolvingagainst the direction of motion of the belt 17b. The scraper 17 operateson the belt after and the scraper 17a before it passes the idler 13.This latter permits the collecting of concentrate by the scraper 17c andthe use of water later to wash off the residue in a separate launder.The use of this scraper 17a. enables the concentrate to be collectedwithout excess water thus if advisable saving subsequent dewatering. Thehopper 14 discharges into the launder 18 or onto a belt except when itis desired to keep the concentrate collected by 17a. separate, in whichcase two launders are used. I

When more water is desirable in the concentrating process, either tofacilitate the washing of the concentrate or to causeincreased'agitation or to speed up the rate of flow in the enclosedchannel,-I introduce jets from nozzles 19, 20and 21 here shown dottedsince they lie behind the plane of the section shown.

The wheel 1 may be driven by a belt\ 24 running on the pulley 25 fast onthe shaft 2 or by other means. It may be pointed out that the forcestending to pass the pulp. through the channel 3 are principally thespouting force of the pulp in the nozzles 9a, 9b, 9c, the force ofgravity acting on the pulp as it passes from the nozzle 9a to the points10 and 12 and the action of the outer surface of the wheel 1, when thisrevolves faster than the pulp. Also the jets from the nozzles 19 and 20.The forces opposing the passage of pulp 1 are friction and eddies andthe movement of the wheel where this is slower than or opposed to thatof the pulp, also the jet from the nozzle 21.

The cover member 4 is comprised of two supporting side pieces 26, Fig. 2and Fig. 3, each carrying a non-magnetic stiffening plate 28 and acurved back 29 (Figs. 1 and 2) which serves to form the outer wall ofthe enclosed channel 3.

This curved cover back 29 is covered with a rub- 'ber lining 30 (Figs. 2and 3 which takes wear and of the wheel including the magnet windingsmay,

be more clearly seen in Figs. 2 and 3. The wheel 1 includes side plates31 each bolted to a hub 32 Fig. 1, secured on the shaft 2, intermediateplates 33, 34 and spacing rings 35, 35, 35. The intermediate plates 33,34 are of steel and are annular in form, each being. clamped between twospacing rings 35, 35 by through-bolts 36, 36. The

plates 31, 33, 34 and the rings 35 are all of magnetic material, therings 35, preferably of cast iron and the plates of steel of goodmagnetic quality. I

Coils'of magnet wire 37, 38, 39 are placed in the open spaces betweenthe plates 31, 33, 34 and are wound onthe rings 35. They serve toproduce the. magnetic flux required for the operation. Connectionsbetween the coils may be made at the points 40 on the outer surface sothat the coils may be conveniently separated for disman- .tlingpurposes. In this case it is desirable/ to wind each coil in two halveswith the connections between the halves at the bottom as shown at 41.The lead of coil 37 may be taken out through the plate 31 at 42 asshown. The leads may be taken to the shaft and connected to a supply inthe well known manner through slip rings. I prefer to wind the coils 37and 38 in one direction and coil 39 in the opposite direction. Fig. 2shows only one half of the construction, the center line 0, c, being thecenter plane of the wheel in the plane of rotation. The section of thewheel lying to the left of the center line (not shown in the figure) isa duplicate of that shown to the right, as will be clear to thoseskilled in the art. The inside coil in the left hand half (not shown) iswound in the same direction as the corresponding coil 39 and the twooutside coils in the left hand, corresponding to 37 and 38, are wound inthe same direction as the latter. The effect of this arrangement ofwindings is to cause coils 37 and 38 to produce an independent magneticcircuit which includes the adjacent plates 31 and 34, the spacing rings35, 35 lying below these coils and the pole pieces 43,44, 45, Fig. 4,lying outside the coils 3'7 and 38. Since the coils 3'7 and 38 are woundin the same direction the plate 33, Fig. 2, will carry little or nomagnetism, as will be understood. Similarly the two corresponding coilsin the left hand half of the wheel will produce asingle magnetic circuitof their own. The two center coils of which coil 39 is the right handcoil will produce a third magnetic circuit. the direction of themagnetism in the third being in the opposite direction to that in theother two. The plate 34 and the corresponding plate in the other halfeach acts as a part of both the two adjacent magnetic circuits andcarries a double quantity of magnetism.

It should be explained that there is a nonmagnetic plate 47 the fullwidth of the wheel (Fig. 3) placed over the coils to protect them. Thisplate 47 bears on the outside of all the plates 31, 33, 34 and isscrewed to them. To make a still better seal a rim piece 31a (Figs. 2and 3) of non-magnetic material such as brass is screwed to the plate 31and the plate 4''! screwed and brazed to it as shown in Fig. 3. The ironpole pieces 43 to 46 (Fig. 4) are shrunk on top of this plate and aresecured to the edges of the plates 31, 33, 34 by the same screws thathold the plate 47. By this construction is secured a very rigid wheelthoroughly protected windings, good magnetic conditions and easyassembling. The rim of the wheel as a whole just described is carriedfrom the hubs 32 (Fig. 2) by the two side plates 31. For purposes ofventilation and general access, openings 71, 71 are provided in theplates 31 as shown in Figs. 1 and 5. The conditions in my apparatus arefavorable for cooling the ma net coils for they are in close contactwith large bodies of metal which are exposed to strong air currents onaccount of the rotation of the wheel. The plates 33 help materially inwithdrawing heat from the windings. The shapes of the pole pieces areshown in Fig. 4, which is a view looking at the face of the wheel. Theair gaps of the magnets extending around the wheel are shown at 48, 48.These air gaps are the locations at which the intense magnetic fieldrelied upon to attract the magnetic material is largely concentrated.The special zigzag shape of the air gaps serves to give a betterdistribution of magnetic field and to increase its total quantity, onaccount of the greater total cross section of the air gap secured. Itmay be noted that there are two air gaps 48, 48 in series for eachmagneticcircuit.

In certain cases where conditions are not so exacting the pole piecesmay consist of straight strips fastened symmetrically on the plates 31,33 and 34 as shown in Fig. 8, the air gap 48a corresponding to the airgap 48 and the pole pieces 43a, 44a and 45a to the pole pieces 43, 44,45. Similarly with the other air gaps and pole pieces.

In Fig. 3 is shown in brass guard piece 49, with a groove to receivedetail the seal at the outer edge of the channel 3. It consists of a aflange 50 on the belt 5 and. a recess to take the rim 51 of the rimpiece 31a. The stifiening plate 28 extends inwardly to cover the end ofthe rim 51 as shown. As the belt 5' and the rim 51 are rotating pieceswhile the guard piece 49 andthe stiffening plate 28 are stationary, asufficient clearance must be left between them at the seals at the sidesof the enclosed channel as shown in Fig. 3.

The curved cover back 29 and the side pieces 26 being of wood I supportthe guard piece 49 from the metal stifiener plate 28 by screws orotherwise.

The corrugated lining 30 is shown in Fig. 7, the direction of flow ofthe pulp being that shown by the arrow. The shape of the corrugationsshown is for the purpose of causing transverse eddies in the pulp streamwithin the enclosed channel 3 (Fig. 3) so that all magnetizableparticles in the stream may be'brought repeatedly in close contact withthe magnetic field giving an opportunity for them to become attracted tothe belt. This is often important because the attractive force of themagnetic field will be much greater near the pole pieces than at adistance and small difierences of distance may be important. While thestrongly magnetizable particles are easily attracted it is only by meansof very strong magnetic fields that the weakly magnetizable particlesmay be held. For this purpose a magnetically favorable apparatus hasbeen here devised and large magnetizing currents are provided. It isfurther best to use as thin a belt 5 as practicable as the nearer thepulp approaches the pole pieces the stronger will be the attraction.

A further advantage of the corrugations is the washing effect of theeddies-in the pulp stream. By a thorough agitation and washing theparticles of gangue slime lodged upon and among the magnetizableparticles are disposed of. In some cases, however, it is more favorableto omit the corrugations and suppress the eddies to prevent the washingaway of too large a portion of the weakly magnetizable particles.

In Figs. 1, 5 and 6, I have shown certain details of the means used forthe support and adjustment 'of the cover member 4. This member is madeadjustable for the purpose of permitting the control of the dimensionsofthe enclosed channel. The position of this element 4 is fixed radiallyin relation to the shaft 2 by means of adjustable rods 52a, 52b, 520,secured at one end to the stiffener plates 28 (Fig. 3) by the members 53and at the other end to a plate 55 centered on the bearing box 27, bythe members 54, 54, 54.

In the construction shown the members 53 and 54 have Tight and'lefthanded internal screw threads and the rods 52a, 52b, 520 are providedwith corresponding exterior threads. The lock nuts 59, 59 serve to lockthe rods in position. Since the rods'52a, 52b, 52care separatelyadjustable the channel 3 (Fig. 3) may be given a varying depth atdifierent points. For example by changing the length of the rod 52a arelatively greater or less depth of slot may be obtained at the top.Similarly by changing the length of the rod 520, a relatively greater orless depth can be secured at the discharge point 10. By changing thelength of the rod 52b a relatively greater or less depth is secured atthe intermediate parts or the enclosed channel.

The velocity of the pulp stream and its turbulence are affected by therelative depth of the channel 3. The width remains fixed in allpositions. The lessening of the depth of the channel means a tendencyfor an increase of velocity and a change of turbulence. It furtheroffers a control of the centrifugal force acting on the pulp streamwhich tends to separate the pulp stream from the belt 5. The effectsproduced by variations in the depth of channel may be very complex anddifferent under one set of conditions and with one type of ore fromother conditions and with other ores and I prefer to try out the bestadjustments under working conditions with the means that I havedescribed and it is possible readily thus to determine the bestadjustment of the cover member 4.

The cover member 4 is kept accurately in a fixed position relatively tothe plane of rotation of the wheel 1 by' the two guides and 61, movingin guide slots 62 and 63. These guides are mounted on plates 70, (Figs.5 and 6) secured across the back of the cover member 4 as shown. Theseguide slots are formed in an A shaped vertical member 64. This member 64is bolted to a foundation 65. It also carries a boss 66 which isconnected by an adjustable hinged rod 67 to the guide ,61. This rod isadjustable by means of right and left hand threadsas is well known. Twolock nuts 69, are provided on the rod 67. The position of the covermember 4 circumferentially is determined by this rod 67. This-adjustmentmay be important andthe best position may be determined by trial. When achange in the position of the entrance to the channel is required due toa change in the position of the jet at 9a, or due to change in spoutingvelocity of the pulp stream or velocity of wheel 1, or otherwise, thisadjustable rod 67 may be used.

In some cases I prefer to use a different construction of magnets asshown in Figs. 9 and 10. This construction has some elements verysimilar to that of the revolving field of an electric generator. Therevolving element has a cast iron 'rim '73, carrying radially extendingmagnetic cores 74, 74. Around these cores are magnetizing coils 75, '75which may be connected in series as shown at 72. Over the pole piecesand the coils is placed a plate of non-magnetic material 76 secured atthe sides of the rim to box plates 18, the coilsbeing thus tightlyclosed and protected. Pole pieces '7'? which are alternately north andsouth are placed above the cores outside the plate '76 and overhangingthe cores as shown. This produces air gaps '79, 79. A belt 5a rides onthese pole pieces corresponding to belt 5 of Figs. 1, 2, 3. This typeofconstruction produces lines of magnetism across the face at rightangles to the plane of rotation, which sometimes has a favorable effecton the concentrating process. 1

The operation may be described as follows:

A supply of wet pulp containing ore or other material, a portion ofwhich is magnetizable, preferably finely ground and carried in an excessof water is continuously supplied to the head tank at a sufiicient rateto cause an overflow at .8, Fig. 1, and a constant hydrostatic head inthe tank. This will cause a flow of pulp out of the three nozzlesat aconstant velocity. Assuming that the wheel 1 is revolving with the jetsand ata higher velocity the wet mixture and the solid particles thereinwill be spread on the surface of the wheel within the channel and anopportunity given for the magnetizable particles to become fixed uponthe belt. Since the belt is going faster than the pulp there will be arelative passing of the pulp over the belt and the solid particles willthus pass near the large number of strong spots and weak spots in themagnetic field produced by the iron pole pieces which lie under thebelt. There will-be a tendency for the pulp to slow down somewhat onaccount of the friction and because the cover back is stationary. Thistendency is resisted by the effect of gravity acting on the pulp as itgoes lower on the wheel. If it is found advantageous the pulp may bemade to slow down and it will then occupy a larger portion of the spacein the channel and may even fill the channel entirely. If there is stillgreater slowing down the volume of pulp within the channel at any onepoint will tend to be greater and an internal pressure might develop.This would result in a tendency for a leakage of pulp on the sidesthrough the seal partsiand-this would be objectionable, if in excess.The difficulty can be remedied by increasing the depth of the channel atthis point either by the adjustments provided or by the originalconstruction of the cover back 29. If the set up of the apparatus issuch that the velocity of pulp increases at any point in the channel thechannel may be made of less depth at that point and the pulp will bekept in closer relation to the belt.

When the pulp has reached the point of discharge of the wastematerial'practically every magnetizable particle will have had manychances to adhere to or become fixed upon the belt and most wasteparticles will have been'washed out from the adhering or fixedconcentrate. At this point the ending of the cover back and the channelpermits the waste to drop by gravity and through the action ofcentrifugal force from the belt and into the waste launder where it maybe further treated if desired. After the discharge of the waste theconcentrate under the influence of the magnetic field remains fixed onthe belt and is carried past the partition 11. The concentrate may thenbe subjected to washing byclean water to remove the gangue adhering toit also muddy water that remains in it. As the attraction of themagnetic field is still effective there is little tendency to wash offany magnetizable particles and the metal content of the concentrate isimproved.

After the concentrate which is still fixed on the belt has passed theclean water nozzle 22 at 12, the belt leaves the wheel at a certainpoint carrying the concentrate outside the influence of the magneticfield, thus allowing it freedom to drop. On account of its wetness,however, there will be a tendency for-the concentrate to stick to thebelt and it may be washed ofi by the jets 15, 15, 16, 16 or may bebrushed ofi by the scraper 17 or 17a. In this case the concentrate wouldnot be mixed with excess water which action would in some cases befavorable from the point of view of dewatering.

If the wheel 1 instead of revolving at a speed greater than the spoutingvelocity of the pulp, revolves at a less velocity, there will be aquieter action with less tendency for the washing oil from theirposition on the belt of the weakly magnetizable particles and generallya slower passage of pulp through the channel, giving more time for themagnetic field to act and other advantages. The minimum agitation willoccur when .the velocity of the wheel and that of the pulp pulp isspread relatively thin over a. large belt area facilitating washing, butwith a slower speed of wheel, the layer will be thicker, giving arougher surface and in some ways favoring the effectiveness of themagnetic field on account of the strengthening effect of themagnetizable material lying on the belt in concentrating the field atthe critical points.

This operation is very favorable from many points of view. The channel 3where the concentration or magnetic attraction occurs is relatively verylong giving ample opportunity for the complete selection of themagnetizable material. so that high velocities may be used. It isfurther a confined or closed space so that the pulp is under control andcan be made to pass slowly or rapidly or to pass in a relatively quietmanner or very turbulently by the means already described. A criticalfactor is the conditions under which the waste is finally separated fromthe concentrate at the end of the channel. If the separation is madewith the pulp emerging at slow velocity and low turbulence there will belittle tendency for the washing away of the weakly magnetizableparticles or particles ad-- hering to the belt at unfavorable points,and this while still permitting the effective washing at earlier partsof the path through the channel. These characteristics and the generalconstruction shown are such that the passage of pulp at high velocitiesmay be availed of and good sized channels used so that a large capacityoutput can be satisfactorily handled. Furthermore, the many adjustmentsincluding those in the control of the pulp feed to the wheel permitsecuring the best results with many different types of ore and processesof ore preparation.

The construction of the iron pole pieces is particularly favorable asthey permit many variations in thedistribution of the magnetic fieldover the surface of the wheel and they may be readily interchanged andremoved or repaired. The stray magnetism is greatly limited. Furthermorethe magnetic field isapproximately uniformly distributed over thesurface of the wheel on the average and once a magnetizable particleadheres to the belt its magnetic condition is not changed during itspassage through the channel until the belt leaves the wheel at 12.Heretofore magnets fixed in position have often been used inside amoving non-magnetic shell and material held on the outer surface of theshell, but such particles as they pass by the magnet poles are subjectedto a varying magnetic field and may pass through weak points in thefield resulting in a tendency for the weakly adhering particles to belost, this is a very important advantage of the invention describedherein.

I may estimate that the advantages of my construction are such that in24 hours in excess of a thousand tons of favorable crude ore can beconcentrated in a single apparatus constructed approximately as thatshown in which the wheel is only a few feet in diameter. On account ofthe very favorable magnetic conditions attainable in my apparatus, veryfine material and materials having only slight magnetizability can beconcentrated.

In certain of the figures such as Fig. 5, and others, certain parts areomitted for the purpose of showing other parts more clearly. This willcarrying surface together with a continuous sheet but is useful wherevermaterial, responding to the influence of a strong magnetic field, is tobe separated from material not so subject or not so subject to the samedegree. The invention shown as operating with wet pulp may be equallywell used with dry mixtures and the magnetizable material will besegregated.

'I claim as my invention.

l. A magnetic separator, comprising a revolving magnetized wheel, havingpositive and negative pole pieces circumferentially disposed andsubstantially uniformly distributed over the outer circumference of saidwheel, a non-magnetic belt running on said pole pieces, means forfeeding a stream of liquid pulp onto said belt in a thin layer the pulpflowing on top of and in contact with the belt on whose surface themagnetic material is collected by the magnetic field through apredetermined operating range, and means for separately controlling thespeeds of said pulp, and said belt to produce a relative velocitybetween them and thus causing the liquid pulp to continuously wash thelayer of magnetizable material as it gathers on the belt under themagnetic influence.

2. A magnetic separator comprising a magnetized wheel having positiveand negative pole areas distributed over the surface, 'a non-magneticbelt running on the surface of said wheel covering said pole areas,means for feeding a liquid mixture of magnetizable and non-magnetizablematerial onto said belt and for maintaining said mixture in contact withsaid belt through the operating range of said pole areas, said feed ingoperation being spread along over a portion of said operating range,said belt cooperating with the influence of said pole areas toaccumulate a thin layer of magnetic particles from said mixture andmeans for maintaining a relative velocity between said belt with itsthin layer of captured particles and the liquid, thus securing acontinuous washing of the magnetizable par- 4 ticles as deposited andpreventing the overlaying of nonmagnetizable particles temporarilycarried with the magnetizable particles by later captured magnetizableparticles.

3. A magnetic wheel for concentrating magnetic ore or similar mixtures,comprising a shaft, a plurality of steel discs, arranged around andsupported from said shaft, -a plurality of circular magnetizing coilsdistributed between said steel discs, magnetizable filler rings placedinside said coils and between said discs and contacting with said discs,means for clamping together said discs and filler'pieces, a water tightcovering secured on the outside of said discs and coils andcircumferential magnetic pole pieces secured outside and upon said watertight covering and serving as a belt carrying surface.

4. A magnetic wheel for concentrating magnetic ores and similarmixtures, comprising. a shaft, a plurality of annular steel discsarranged around and supported from said shaft, a plurality of circularmagnetizing coils distributed between said discs, magnetizable fillerrings located inside said coils and between said discs and contactingwith said discs, means for clamping together said discs and fillerpieces, and circumferential ma netic pole pieces secured to the outsideedges of but spaced fromsaid discs and serving as a belt of non-magneticmaterial inserted between said pole pieces and the edges of said discs.

5. A magnetic wheel for concentrating magnetic ores or similar mixtures,comprising a shaft, a

plurality of annular steel discs, arranged around and supported fromsaid shaft, a plurality of circular magnetizing coils distributedbetween said discs, said coils being in pairs and those of a. pair beingseparated by an additional disc, magnetizable filler rings locatedinside said coils and between said discs and contacting with said discs,means for clamping together said discs and filler pieces andcircumferential pole pieces secured to the outside edges of said discsand serving as a belt carrying surface, the magnetic flux in adjacentfirst named discs being in opposite directions.

6. A magnetic wheel for concentrating magnetic ores and similarmixtures, comprising a shaft, a plurality of annular ste el discs,arranged around and supported from said shaft,- a plurality of circularmagnetizing coils distributed between said discs, magnetizable fillerrings located inside said coils and between said discs and contactingwith said discs, means for clamping together said discs and fillerpieces, and circumferential magnetic pole pieces secured to the outsideedges of said discs and servingas a belt carrying surface, together withunmagnetized intermediate discs located midway between said annulardiscs and dividing said coils and said filler pieces and carryingauxiliary pole pieces secured to the outer edge of said intermediatediscs, each lying between and cooperating with two'of the first namedpole pieces.

7. A magnetic separator, comprising a magnetic wheel having positive andnegative magnetic pole areas distributed over the surface, anon-magnetic belt running on the surface of said wheel covering saidpole areas, means for feeding a liquid mixture of magnetizable andnon-magnetizable material onto said belt and for maintaining saidmixture in contact with said belt through the operating range of saidpole areas, said feeding operation being distributed along over aportion of said operating range, said belt cooperating with theinfluence of the magnetic pole areas to accumulate a thin layer ofmagnetizable particles from said mixture and means for maintaining arelative velocity between said belt with its thin layer of capturedparticles and the liquid, while in contact therewith, thus securing acontinuous washing of the captured magnetic particles as deposited andpreventing the admixture of nonable particles by later capturedmagnetizable particles.

8. A magnetic concentrator, comprising a revolving magnetic wheel, anon-magnetic belt riding thereon through a working range of magneticaction and means for feeding a liquid mixture of magnetizable andnon-magnetizable particles onto and against said belt, for washingconcentrate on the surface of said belt and for distributing said feedthrough a portion of the working magnetizable particles carried with themagnetizrange, whereby opportunity is offered for the PERCY H. THOMAS.

